Many liquids are used commercially and stored in various containers ready for use. The liquids can be mixtures of liquids having different densities so that they will tend to settle one from another, and also liquids which contain fine particulates which will settle out of the liquid if left for long periods of time. It is therefore necessary to provide some form of mixing so that the liquids will be homogeneous at the time that they are required for use, for instance, in an industrial process.
Various forms of apparatus have been provided for mixing liquids and these include devices to shake or rotate the container of liquid, as well as intrusive devices which are placed in the liquid and caused to vibrate or rotate in the liquid. Such devices must meet a number of design criteria. First of all, because the cost of mixing is directly related to the horsepower consumed in performing the operation, the mixing should be done efficiently to keep the costs down. Also, because it may be necessary to minimize the time of mixing to match the requirements of a continuous process, the actual time used for mixing becomes important.
The present invention is of the intrusive type intended to be placed in the liquid and caused to rotate to create flow within the liquid which will result in mixing.
In some mixing applications, an intrusive impeller must be entered through an opening in a container. An example of this would be liquid in a drum. The impeller has to be engaged through the opening or "bung hole" of the drum. Some attempts have been made to do this using impellers which consist essentially of a folding propeller. The opening in the drum is quite commonly near the wall of the drum and consequently the propeller must be placed away from the wall to avoid contact when the propeller is driven; the structure which drives the propeller must be supported such that the propeller will not drive itself into the wall.
Another form of mixing impeller can be found in U.S. Pat. No. 5,314,310 to Bachellier. In this patent, a rather complex welded structure has a generally frusto-conical body having blades which are angled and welded in place in a frame. The structure is complicated and is more suitable for larger impellers rather than for the smaller variety used in drums and the like.
In general, prior art impellers used for mixing liquids tend to be complex and expensive to manufacture, especially in smaller sizes. Also, complex structures tend to have places where material can collect making such structures difficult to keep clean and therefore unsuitable for use in some industries, notably the food industry.
It is therefore an object of the present invention to provide a simplified impeller which is relatively inexpensive to manufacture and which is suitable for mixing smaller volumes of liquids such as those found in drums and other containers, and to provide efficient mixing.